The Wright brothers' critical insight was the importance of "lateral stability" - that is, wingtip-to-wingtip stability - to flight. And their great innovation was something they called "wing warping," in which they used a series of pulleys that caused the wingtips on one side of the airplane to go up when the wingtips on the other side were pulled down. That allowed the Wrights' airplane to make banked turns and to correct itself when it flew into a gust of wind.

But when the Wrights applied for a patent, they didn't seek one that just covered wing warping; their patent covered any means to achieve lateral stability. There is no question what the Wrights sought: nothing less than a monopoly on the airplane business - every airplane ever manufactured, they believed, owed them a royalty. As Wilbur Wright, who was both the more domineering and the more inventive of the two brothers, put it in a letter: "It is our view that morally the world owes its almost universal system of lateral control entirely to us. It is also our opinion that legally it owes it to us."

Even though Wrights' competitor Curtiss developed an entirely different system to achieve lateral stability (the ailerons airplanes use to this day), the Wright brothers still believed Curtiss owed them money for it. The legal standoff that ensued in the US airplane industry at the time halted all innovation, so much so that when the WWI broke out, the US government had to step in to force airplane manufacturers to cross-license their patents.